The present invention is suitable for producing a variety of cheeses (designated herein as "stirred curd" cheeses), including American style cheeses, such as current manufacture, cheddar, Colby, American, and other washed curd varieties; Italian style cheeses, such as mozzarella, pizza cheese, Parmesan, Romano, and provolone cheeses; semi-soft cheeses, such as brick, Edam, Gouda, Muenster, Monterey Jack, and pepper jack; and Swiss varieties, such as traditional Swiss, baby Swiss, and Jarlsberg cheeses. It is suitable for salting any type of food product, including these and other types of cheeses. Cheesemakers have strong financial incentives to ensure that these cheeses are made up of uniform sized curds and have moisture levels that fall within specific ranges prescribed by government and industry bodies. In the United States, the United States Department of Agriculture (U.S.D.A.) prescribes the ranges for each type of cheese. The cheese moisture level is greatly affected by salt content and distribution.
For about the last twenty-five years, stirred curd cheeses have been produced in large, open, tub-like curd tables. Curd tables have vertical agitators mounted on an assembly above the table. As the assembly moves back and forth above the table, the cheese curds are mixed. The vertical agitators ensure that the curds, when mixed, are of uniform size. Thomson, U.S. Pat. No. 3,490,751, issued Jan. 20, 1970; Naulin, U.S. Pat. No. 1,499,026, issued Jun. 24, 1924; and McKinnon, U.S. Pat. No. 794,421, issued Jul. 11, 1905, disclose assemblies that stir cheese curds.
Curd tables have serious disadvantages, however. First, making stirred curd cheeses on a curd table is a labor-intensive process. The cheesemaker must start with an empty table, and then fill it with curds and whey. As the curds are mixed and processed, salt must be added to the curds by hand at the proper point in the processing. After mixing and processing the curds, the agitator attachments are removed and replaced with attachments that scoop the product from the table. Because the assembly can remove the product from the curd table only in small scoops, and cannot remove it all at once, the process of removing the curds is time consuming and labor-intensive. To make matters worse, because the assembly is not able to remove curds from the corners and edges of the curd table, after the assembly has been used to remove most of the curds the cheesemaker manually must remove the product that remains in the corners and edges of the curd table. Further, because some curds must sit for longer periods of time than others during the removal process, it is difficult to ensure that moisture levels are uniform in all of the curds. Specifically, because moisture is lost as the curds sit, the curds that are removed earlier will have a higher moisture content than those that are removed later.
In addition, the sequential nature of cheese curd processing on a curd table makes it difficult to obtain uniform salt concentrations and consistent levels of acid development. Bacteria are added to obtain the proper acid levels in the cheese; the acid develops at a rate that is a function of the amount of bacteria added and the time the bacteria are allowed to work. When the acid level is within the desired range, users of the curd table must spread salt over the curds manually. Because the salt is distributed by hand, uniform salt dispersion is inherently difficult; and because it takes several minutes to distribute salt over the curds, curds that are salted first are salted at an earlier stage of acid development than are those that are salted later. In addition, because it takes the cheesemaker several minutes to apply salt to the curds, the salt is not applied at a single point in the process. The result of these difficulties is that the acid development and moisture content of the curds are not uniform. Finally, this salting process also is labor-intensive, and inconsistent salt concentrations result because the quantity of cheese delivered from the vat to the curd table may vary from batch to batch.
Curd tables have other disadvantages, as well. Because the tables are open, the curds are exposed to airborne contaminants, the rate at which process heat is lost cannot be controlled, and moisture is lost into the atmosphere. Furthermore, the agitator assemblies are complex and require significant maintenance. In addition, curd tables drain the whey from the curds by means of a mesh screen at the bottom of the table. As the curds are mixed, however, they are pushed across the screen repeatedly, which effects a grating action on the curds. This grating action causes small particles, called curd fines, to be lost from the curds and pass through the screen, thus reducing yields.
When compared to curd tables, conveyor belt systems save labor. The belt systems that currently are in use were developed approximately fifteen years ago. They use horizontal agitators, which have sharp prongs that physically alter the curds by knitting them together and then grinding them up. Latimer et al., U.S. Pat. No. 4,538,510, issued Sep. 3, 1985, and Brockwell, U.S. Pat. No. 4,309,941, issued Jan. 12, 1982, disclose conveyor belt systems with horizontal agitators. Although systems with horizontal agitators are suitable for some types of cheeses, they are not suitable for processing stirred curd cheeses because they physically damage the cheese curds and cannot produce uniform sized cheese curds.
Horizontal agitator systems also have several inherent processing disadvantages. When the curds and whey are dispensed onto the conveyor belt, the mixture is of varying depths or thicknesses. Horizontal agitators are not able to level the mixture across the width of the belt, so mixing is not uniform. Furthermore, because the horizontal agitators tend to grind the cheese, they produce curd fines, thus reducing yields and causing profits to be lost. Also, because horizontal conveyor systems produce curds of different sizes, moisture content and salt penetration varies from curd to curd.
There also are disadvantages to the oscillating boom salting apparatuses currently used with conveyor belt systems. First, oscillating booms consist of many moving parts, and thus are expensive to manufacture and to maintain. More important for cheese processing purposes is that the booms apply more salt to the food at each end of the oscillation cycle, and thus do not apply salt to the curds in a uniform manner.
These salting problems are exacerbated by the use of the horizontal agitators with conveyor belts. Because the horizontal agitators cannot level the height of the curds across the width of the belt, the salt concentration varies based on the height of the curd mass where the salt is applied. Furthermore, horizontal agitators are unable to mix the salt uniformly across the width of the belt, and instead tend only to push the salt in the same straight-line direction in which the food already is travelling on the conveyor belt. In addition, horizontal agitators spin in a single location, so they are not effective for stirring the food.
Horizontal agitator systems also have sanitation problems. The bearings used with horizontal agitators are subject to large loads, and the bearings wear out and begin to leak. Conversely, cleaning materials may leak into and damage the bearings. Significant maintenance is required to detect and correct leakage problems as soon as they occur.
Neither the curd tables nor the conveyor belt systems provides a mechanism for monitoring the moisture level of the cheese curds. The moisture levels therefore cannot be measured until the next day. Because the moisture levels in fully processed cheese cannot be adjusted, if the moisture levels fall outside prescribed parameters, the entire previous day's production of cheese must be disposed of at less than fair market value for that type of cheese.
There is an unmet need for a food processing device that allows processing of large quantities of stirred curd cheeses while maintaining the physical consistency and integrity of the curds, and at the same time solves the timing problems associated with curd tables and reduces the amount of labor required to process the cheese curds. It further would be desirable if the food processing device had a mechanized salting apparatus that did not have moving parts, but that did spread the salt evenly over the food being processed and in proportion to the amount of food being processed.